I. Field of the Invention
The present invention relates to the field of exhaust gas recycling systems for use in combination with internal combustion engine.
II. Description of the Prior Art
Conventional pressure control exhaust gas recycling systems typically include a valve for regulating the amount of exhaust gas recycled (hereinafter sometimes referred to as EGR) and a pneumatically actuated control means coupled to the intake manifold in order to actuate the valve mechanism in response to the partial pressures developed within the intake manifold. By such conventional prior art apparatus the amount of exhaust gas recycled (EGR) is generally directly proportional to the amount of engine air intake. Therefore, the ratio of EGR to air intake has been substantially level under all running conditions of the engine.
However, since an internal combustion engine typically generates a high power output when the amount of air intake is large, such as under heavy loads or high RPM operations, it is necessary, in order to achieve fuel economy and to observe the limited heat resistance of typical EGR control parts, to reduce the EGR ratio to zero or at least a substantially low volume whenever the amount of air intake is large. Clearly, in the conventional exhaust gas recycling system, where the amount of exhaust gas recycled is proportional to the amount of air intake, such conventional systems have been unable to respond to this desired fashion. In fact, the EGR ratio of such conventional systems is usually dependently fixed on the running conditions of the engine.
What is needed then is an exhaust gas recycling system for internal combustion engines which improves performance, decreases fuel costs, and protects EGR control parts by reducing the EGR ratio whenever the amount of engine air intake exceeds a predetermined level.